Pyrometers are used in gas turbine engines to measure the high pressure turbine blade temperatures using infrared optical detection techniques. Because of the proximity of the gas turbine combustor to the leading edge of the high pressure turbine in a gas turbine engine, extremely hot gases exiting from the combustor create a pyrometer signal which is cluttered with positively biased noise. This unwanted noise is due to high frequency combustion transients (hot combustion products, e.g. carbon particles) passing in front of the pyrometer's field of view. The hot particles emit light in the same infrared spectrum to which the pyrometer is sensitive, but at a much higher intensity which tends to obscure the light emitted by the cooler turbine blades. At the upper power settings of the engine, the quality and frequency of the clutter is so dense that very few blades, if any, are visible on any single rotation. Thus, a method of acquiring the blade temperature data from the cluttered pyrometer signal is needed.
Known pyrometer signal averaging techniques (usually analog) used in the past are incapable of identifying individual blade temperature anomalies and tend to give erroneous high readings in the presence of positively biased clutter. This has the undesirable effect of unnecessarily reducing thrust at high power demand. This invention allows for detection of hot (clogged) and cold (broken) blades, and the clutter rejection algorithm which is used allows for determination of an unbiased average turbine temperature in the presence of positively biased clutter.